Ultrasonic transducer arrangement for a clamp-on ultrasonic flow measuring point and a clamp-on ultrasonic flow measuring point and method for commissioning the clamp-on ultrasonic flow measuring point

ABSTRACT

An ultrasonic transducer arrangement for a clamp-on ultrasonic, flow measuring point includes a plurality of ultrasonic transducers, each adapted to radiate ultrasonic signals into the measuring tube and/or to receive ultrasonic signals emerging from the measuring tube, wherein a first group of first ultrasonic transducers is arranged on a first side of the measuring tube, and a second group of second ultrasonic transducer is arranged on a second side of the measuring tube opposite the first side, wherein at least one first/second ultrasonic transducer is adapted to receive ultrasonic signals of at least one second/first ultrasonic transducer, respectively, wherein adjoining ultrasonic transducers of the first group have, in each case, first separations from one another, and wherein adjoining ultrasonic transducers of the second group have, in each case, second separations from one another.

Clamp-on ultrasonic, flow measuring points are applied instead of inlineflow measuring points with ultrasonic transducers integrated into ameasuring tube, when an installation of a measuring tube of an inlineflow measuring point is cumbersome or impossible. Clamp-on ultrasonic,flow measuring points are significantly easier to set up and can beinstalled on different measuring tubes. They have, however, thedisadvantage that ultrasonic transducers of such a measuring point as itcomes from the factory can, at most, be only roughly tuned to oneanother.

The state of the art shows ultrasound transducer arrangements of suchflow measuring points, in the case of which the ultrasonic transducersare mounted shiftably relative to one another, in order to permit a finetuning. This requires, however, technical knowledge and also a certaintime consumed. A detouring around this problem is presented inDE102008029772A1, in the case of which two groups, in each case, of aplurality of ultrasonic transducers are placed on an outside of ameasuring tube, wherein adjoining ultrasonic transducers of each grouphave small separations from one another, wherein these separations areslightly different between the groups. In this way, it is achieved thatdue to a plurality of ultrasonic transducers in many cases an ultrasonictransducer pair connected by an ultrasonic signal path exists and, thus,small changes of process parameters, such as, for example, velocity ofsound, can be compensated by changing the ultrasonic transducer pair.

An object of the invention is to provide an ultrasonic transducerarrangement for a clamp-on, ultrasonic, flow measuring point and aclamp-on ultrasonic, flow measuring point, in the case of which theultrasonic transducer arrangement is largely independent of measuringtube diameter.

The object is achieved by an ultrasonic transducer arrangement asdefined in independent claim 1, as well as a clamp-on ultrasonic, flowmeasuring point as defined in independent claim 8, and a method forcommissioning the ultrasonic, flow measuring point into operation asdefined in independent claims 11, 14 and 15.

An ultrasonic transducer arrangement of the invention for a clamp-onultrasonic, flow measuring point based on the travel time differenceprinciple comprises:

a plurality of ultrasonic transducers, which are adapted to be arrangedon an outside of a measuring tube of the clamp-on flow measuring point,

wherein the ultrasonic transducers have, in each case, at least onetransducer element for producing and/or receiving ultrasonic signals aswell as a coupling element, wherein the coupling element has a firstcontact area and a second contact area, wherein the transducer elementis arranged on the first contact area, and wherein the ultrasonictransducer is adapted by means of the second contact area to becontacted with the measuring tube,

wherein the ultrasonic transducers are adapted to radiate ultrasonicsignals into the measuring tube and/or to receive ultrasonic signalsemerging from the measuring tube,

wherein the second contact areas have, in each case, a normal, whereinthe normals define a plane, in which ultrasonic signal paths of theultrasonic signals extend,

wherein a first group of first ultrasonic transducers is arrangedrelative to a measuring tube longitudinal section on a first side of themeasuring tube, and wherein a second group of second ultrasonictransducers is arranged relative to the measuring tube longitudinalsection on a second side of the measuring tube lying opposite the firstside,

wherein the coupling elements of the first ultrasonic transducers andsecond ultrasonic transducers have, in each case, a longitudinal axis,wherein the longitudinal axis has, in each case, an interior angle a atthe corresponding second contact area, wherein the ultrasonic signalpath extends in the coupling element in the direction of thelongitudinal axis,

wherein at least one, first/second ultrasonic transducer is adapted toreceive ultrasonic signals of at least one, second/first ultrasonictransducer,

characterized in that

adjoining ultrasonic transducers of the first group have, in each case,first separations from one another, and wherein adjoining ultrasonictransducer of the second group have, in each case, second separationsfrom one another, wherein the first separation and the second separationare unequal,

wherein 2*A1>=A2>=1.125*A1, and especially 1.75*A1>=A2>=1.16*A1, andpreferably 1.6*A1>=A2>=1.25*A1.

In an embodiment, a relationship between the first separation and secondseparation corresponds to the following equation:

(a+1)*A1=a*A2 with b>a>1, a is a natural number and b is an upper valuefor a range of a and is less than 9, and, especially, less than 7, andpreferably less than 5.

Advantageously, the first number and the second number both equal a+1.

In an embodiment, the first group of ultrasonic transducers has a firstnumber of ultrasonic transducers, and a second group of ultrasonictransducers has a second number of ultrasonic transducers,

wherein:

N1 is greater than or equal to a+1 and especially greater than or equalto a+2,

N2 is greater than or equal to a+1 and especially greater than or equalto a+2.

In an embodiment, the transducer elements have a radial extent rA,wherein rA>3/(4*a)*A1*cos(α),

and especially

rA>1/(2*a)*A1*cos(α).

In an embodiment, the ultrasonic transducer arrangement includes atleast a third ultrasonic transducer, which has a signal path, whichextends perpendicularly to the second contact area.

In an embodiment, the first group of ultrasonic transducers and thesecond group of ultrasonic transducers are held, in each case, by asupport body, which is adapted for positioning and securing theultrasonic transducers.

In an embodiment, the ultrasonic transducers in the support body areeach individually held.

A clamp-on-ultrasonic, flow measuring point of the invention formeasuring a flow velocity of a medium flowing through a measuring tubeincludes:

the measuring tube for conveying a medium and having a measuring tubeaxis,

an ultrasonic transducer arrangement of the invention according to oneor more of the definitions above, wherein the ultrasonic transducerarrangement is oriented in parallel with the measuring tube axis,

an electronic measuring/operating circuit for operating the ultrasonictransducers as well as for ascertaining and providing measured values offlow velocity.

In an embodiment, the clamp-on-ultrasonic, flow measuring point includesa curvature sensor for determining an outer diameter of the measuringtube,

wherein the curvature sensor has a separation sensor and a spacer,

wherein the spacer has a central region and two ends adjoining thecentral region, wherein the ends are bounded from the central region bya bend or an angle,

wherein the spacer is adapted by means of the ends to be contacted withthe measuring tube, wherein the central region is adapted to be spacedfrom the measuring tube, and wherein a cross section, or longitudinalsection, through the spacer through the two ends is adapted to extend inparallel with a measuring tube cross section,

wherein the separation sensor is arranged on the spacer in the centralregion,

wherein the electronic measuring/operating circuit is adapted to operatethe separation sensor.

In an embodiment, the separation sensor is an optical or acoustic,separation sensor.

In a method of the invention for commissioning the clamp-on ultrasonic,flow measuring point into operation,

a plurality of first ultrasonic transducers/a plurality of secondultrasonic transducers transmit, simultaneously or offset in time, ineach case, an ultrasonic signal, which ultrasonic signals are receivedby second ultrasonic transducers/first ultrasonic transducers,

wherein the electronic measuring/operating circuit determines based onsignal strength and/or signal/noise ratio of the received ultrasonicsignals at least one ultrasonic transducer pair to be used for ameasurement operation.

In an embodiment, the ultrasonic signals are quasi continuous and differin frequency, or

wherein the ultrasonic signals are pulsed and differ in the followingfeature:

center frequency of a frequency spectrum.

In an embodiment, a medium is conveyed through the measuring tube,

wherein in the case of received ultrasonic signals ultrasonic signalportions are examined for presence of a travel time difference,

wherein ultrasonic signal portions without travel time difference areexcluded in determining an ultrasonic transducer pair to be used.

In the case of a method of the invention for commissioning theclamp-on-ultrasonic, flow measuring point into operation,

the third ultrasonic transducer is caused to transmit and to receive anultrasonic signal,

wherein the electronic measuring/operating circuit determines an outerdiameter and/or inner diameter based on at least one signalcharacteristic of the received ultrasonic signal,

wherein a usable signal characteristic is, for example:

travel time of a signal reflection.

In a method of the invention for commissioning the clamp-on-ultrasonic,flow measuring point into operation, the electronic measuring/operatingcircuit determines an outer diameter by means of the curvature sensor.

The invention will now be described based on examples of embodimentspresented in the appended drawing, the figures of which show as follows:

FIG. 1 two ultrasonic transducers of an arrangement of the invention;

FIG. 2 geometric relationships of an arrangement of the invention forultrasonic transducers;

FIG. 3 by way of example, an arrangement of the invention for ultrasonictransducers;

FIG. 4 by way of example, an arrangement of the invention for ultrasonictransducers;

FIG. 5 an arrangement in a support body;

FIG. 6 a flow measuring point with an arrangement of the invention;

FIG. 7 a curvature sensor.

FIG. 1 shows a schematic construction of examples of ultrasonictransducers 20 and a part of an arrangement of the invention comprisingtwo, first ultrasonic transducers 20.1 and two, second ultrasonictransducers 20.2, which are arranged on an outside of a measuring tubewall of a measuring tube 2. An ultrasonic transducer includes, in eachcase, at least one transducer element 21, preferably a piezoelectrictransducer element, and a coupling element 22, wherein the transducerelement is arranged on a first contact area 22.1 of the couplingelement, and wherein the coupling element is acoustically andmechanically coupled with the measuring tube via a second contact area22.2. The coupling element has a longitudinal axis L, along which travelultrasonic signals produced by the transducer element 21 or received viathe contact area 22.2. The transducer element is preferably disc shapedand has a radial extent rA. The radial extent of the transducer elementdoes not necessarily correspond to a radial extent of the couplingelement, such that the showing in FIG. 1 simply facilitates the drawing.The longitudinal axis has relative to a normal N of the second contactarea an angle γ, so that ultrasonic signals are coupled inclined intothe measuring tube. In the measuring tube, an ultrasonic signal path hasan angle β to the normal, which angle β, in general, differs from theangle γ, when a velocity of sound in the coupling element differs from avelocity of sound in the medium. Neighboring first ultrasonictransducers 20.1 have a first separation A1 from one another,Correspondingly, adjoining second ultrasonic transducers have a secondseparation A2 from one another.

Typical values for the angle γ are 30° to 45°, depending on thematerials utilized for the coupling element and measuring tube and themedium flowing through the measuring tube.

FIG. 2 shows geometric relationships of an arrangement of the inventionfor ultrasonic transducers, wherein a first group G1 of ultrasonictransducers 20 composed of first ultrasonic transducers 20.1 arearranged on a first side 2.11 in a measuring tube longitudinal sectionof the measuring tube 2, and wherein a second group G2 of ultrasonictransducers 20 composed of second ultrasonic transducers 20.2 arearranged on a second side 2.12 of the measuring tube 2 lying oppositethe first side. The here selected number of, in each case, fiveultrasonic transducers per group is for purposes of illustration and isnot to be construed as limiting.

The first ultrasonic transducers 20.1 have a first separation A1 betweenneighbors, and the second ultrasonic transducers 20.2 have a secondseparation A2 between neighbors, wherein the separations A1 and A2differ from one another. This has the result that in the case ofsuperpositioning of an ultrasonic signal path UP defined by a firstultrasonic transducer with an ultrasonic signal path UP defined by asecond ultrasonic transducer, such as happens for the first and secondultrasonic transducers of the left side, there is no superpositioning ofthe ultrasonic signal paths of the other illustrated first and secondultrasonic transducers. This is pointed out for the second set of firstand second ultrasonic transducers on the left side by a solid line forthe first ultrasonic transducer and an offset dashed line for the secondultrasonic transducer. In the latter case, a signal amplitude of areceived ultrasonic signal registered by a receiving ultrasonictransducer is lower than in the case of a superpositioning of the signalpaths between two ultrasonic transducers.

Since ultrasonic signals have a spatial expansion perpendicularly totheir propagation in the direction of an ultrasonic signal path, anincreasing offset of two ultrasonic signal paths between an emittingultrasonic transducer and a receiving ultrasonic transducer leads to anincreased lessening of the received ultrasonic signal amplitude.

Due to the different separations A1 and A2, there are differentmeasuring tube diameters, at which the ultrasonic signal path of a firstultrasonic transducer 20.1 and the ultrasonic signal path of a secondultrasonic transducer 20.2 superimpose. This is shown with theultrasonic transducers U2 and U5. From this, a maximum relevantultrasonic signal path offset can be derived for the ultrasonictransducer arrangement. This is the case, when a measuring tube diameterhas a value, which lies exactly between two measuring tube diametervalues, at which the ultrasonic signal path of a first ultrasonictransducer 20.1 and the ultrasonic signal path of a second ultrasonictransducer 20.2 superimpose.

Preferably, the transducer elements have a radial extent rA, whereinrA>3/(4*a)*A1*sin(α), and especially rA>1/(2*a)*A1*sin(α), or whereinrA>3/(4*a)*A1*cos(γ), and especially rA>1/(2*a)*A1*cos(γ).

Neglecting an ultrasonic signal expansion, a maximum relevant deviation,in this case an offset, of an ultrasonic signal path in a directionextending along a measuring tube axis, of a third of an ultrasonicsignal width in parallel with the measuring tube axis would result. Ithas been found that, in this case, an ultrasonic signal amplitude in areceiving ultrasonic transducer is still sufficient for good signalprocessing.

Thus, by providing different separations A1 and A2, an ultrasonic, flowmeasurement worthwhile over a large measuring tube diameter range isenabled.

A here neglected wall thickness of the measuring tube 2 influences asound entrance point into the medium relative to the coupling element.Those skilled in the art will, in given cases, take this intoconsideration.

FIG. 3 presents, by way of example, a demonstrative arrangement of theinvention for ultrasonic transducers on a measuring tube 2, wherein theparameter a is selected equal to 3. The inclined lines emanating fromthe ultrasonic transducers U1 to U5 of a first group of ultrasonictransducers show the course of ultrasonic signal paths. The horizontallines display measuring tube diameters, at which ultrasonic signal pathsemanating from the ultrasonic transducers U6 to U10 of a second group ofultrasonic transducers agree with ultrasonic signal paths of the firstgroup of ultrasonic transducers. In order to show the effect ofdifferent measuring tube diameters, the second group of ultrasonictransducers is shown twice. In the case of a small measuring tubediameter, for example, the ultrasonic transducers U4 and U6 can form ausable ultrasonic transducer pair. For large diameters, an outerultrasonic transducer, such as the ultrasonic transducer U5 shown here,can be required, in order to be able to form an ultrasonic transducerpair with an ultrasonic transducer U8 of the other group. Depending onmeasuring tube diameter, thus, different ultrasonic transducers of bothgroups of ultrasonic transducers can be used.

For the first group of ultrasonic transducers having a first number N1of ultrasonic transducers and for the second group of ultrasonictransducers having a second number N2 of ultrasonic transducers,preferably: N1 is greater than or equal to a+1 and especially greaterthan or equal to a+2, and N2 is greater than or equal to a+1 andespecially greater than or equal to a+2. N1 and N2, thus, do not such asshown in FIG. 3 need to be 5 or equal.

The greater is N1, N2, the greater is a measuring tube diameter rangeusable with an arrangement of the invention for ultrasonic transducers.

Those skilled in the art will form ultrasonic transducer arrangementsaccording to their requirements.

FIG. 4 presents, by way of example, an arrangement of the invention forultrasonic transducers with first G1 and second G2 groups of ultrasonictransducers and a third group G3 with a third ultrasonic transducer20.3.

The third ultrasonic transducer is adapted to radiate ultrasonic signalsperpendicularly to the measuring tube wall 2.3 into the measuring tube 2and to receive the ultrasonic signals reflected on an oppositely lyingmeasuring tube side. Using a signal travel time, a measuring tubediameter can be deduced and therewith a usable pair of ultrasonictransducers with an ultrasonic transducer of the first group and anultrasonic transducer of the second group can be selected forcommissioning a clamp-on-ultrasonic, flow measuring point intooperation. Thus, a testing of various ultrasonic transducers of thefirst and second groups can be limited or avoided.

The numbers and orientations of the ultrasonic transducers shown hereare purely by way of example and have demonstrative purposes and are notto be construed as limiting.

FIG. 5 shows ultrasonic transducers of a first group G1 or a secondgroup G2 arranged in a support body 30 and held by such. The supportbody can have positioning elements, by means of which the ultrasonictransducers are positionable in a desired position in the case ofinstallation in the support body. After positioning, the ultrasonictransducers can be potted in the support body. The ultrasonictransducers can, for example, be individually held in the support body,so that a fitting to, for example, a rough or uneven measuring tubesurface is possible. The view is by way of example relative to thenumber and arrangement of the ultrasonic transducers and is not to beconstrued as limiting. Also, such as shown here, a third ultrasonictransducer 20.3 can be arranged in such a support body.

FIG. 6 shows by way of example a clamp-on ultrasonic, flow measuringpoint 1 having a measuring tube 2, an ultrasonic transducer arrangement10 of the invention, a support body 30 for holding the ultrasonictransducer arrangement, a curvature sensor 4 for determining a measuringtube bend and an electronic measuring/operating circuit for operatingthe ultrasonic transducer and the curvature sensor and for providingflow measured values. A clamp-on ultrasonic, flow measuring point doesnot have to have a curvature sensor.

FIG. 7 shows a construction of a curvature sensor 4, by means of which ameasuring tube outer diameter can be determined. With knowledge of themeasuring tube outer diameter and a measuring tube thickness, anultrasonic transducer pair to be used can be predetermined. A curvaturesensor includes a separation sensor 4.1 and a spacer 4.2, which spacerhas a central region 4.21 and two ends 4.22 bent from the centralregion. The spacer is placed on the measuring tube in parallel with across section of the measuring tube 2, wherein the central region has ameasuring tube outer diameter dependent separation from a measuring tubeouter surface. This separation is measured with the separation sensor4.1 applied in the central region. Such a sensor can be, for example, anultrasonic sensor or an optical sensor.

Commissioning the clamp-on ultrasonic, flow measuring point in operationrequires a determining of an ultrasonic transducer pair comprising afirst ultrasonic transducer and a second ultrasonic transducer. To thisend, such as already mentioned, a measuring tube inner diameter as wellas a measuring tube thickness can be determined by means of a thirdultrasonic transducer and, as a result, an ultrasonic transducer paircan be determined. Alternatively or supplementally, also such as alreadymentioned, a curvature sensor can be applied. Alternatively orsupplementally, a plurality of first and/or second ultrasonictransducers can, simultaneously or offset in time, transmit ultrasonicsignals. A selection of an ultrasonic transducer pair can then bedetermined, for example, based on ultrasonic signal amplitude, which ismeasured by means of ultrasonic transducers selected as receivers. Forthe purpose of figuring out which transducers are involved, one or morefeatures can be impressed on the ultrasonic signals of differentultrasonic transducers applied for transmitting ultrasonic signals.

For example, in the case of pulsed ultrasonic signals, a centerfrequency can be characteristic. Alternatively or supplementally, forexample, ultrasonic signals can have different signal chirp.

At start-up, also a medium can be conveyed through the measuring tubeand a travel time difference measurement of ultrasonic signalsperformed. In such case, ultrasonic signals without or with small traveltime difference can be excluded from being taken into consideration.Such signals are, for example, signals, which are coupled from anoriginal ultrasonic signal into the measuring tube, without travelingthrough the medium. In the case of a receiving ultrasonic transducer,thus, emanating from an original ultrasonic signal, a plurality ofultrasonic signals caused by various reflections can arrive superimposedor offset in time.

LIST OF REFERENCE CHARACTERS

1 clamp-on-ultrasonic, flow measuring point

2 measuring tube

2.11 first measuring tube side

2.12 second measuring tube side

2.2 measuring tube axis

2.3 measuring tube wall

3 electronic measuring/operating circuit

4 curvature sensor

4.1 separation sensor

4.2 spacer

4.21 central region

4.22 end

10 ultrasonic transducer arrangement

20 ultrasonic transducer

20.1 first ultrasonic transducer

20.2 second ultrasonic transducer

20.3 third ultrasonic transducer

21 transducer element

22 coupling element

22.1 first contact area

22.2 second contact area

30 support body

N1 first number

N2 second number

A1 first separation

A2 second separation

UP ultrasonic signal path

N normal

U1-U9 ultrasonic transducers

G1 first group

G2 second group

G3 third group

1-15. (canceled)
 16. An ultrasonic transducer arrangement for a clamp-onultrasonic, flow measuring point based on the travel time differenceprinciple, the arrangement comprising: a plurality of ultrasonictransducers, each adapted to be arranged on an outside of a measuringtube wall of a measuring tube of the clamp-on flow measuring point,wherein each ultrasonic transducer includes at least one transducerelement configured to generate and/or receive ultrasonic signals and acoupling element, wherein the coupling element includes a first contactarea and a second contact area, wherein the at least one transducerelement is arranged on the first contact area, and wherein eachultrasonic transducer is adapted to contact the measuring tube therespective second contact area, wherein each ultrasonic transducer isconfigured to radiate ultrasonic signals into the measuring tube and/orto receive ultrasonic signals emerging from the measuring tube, whereinthe second contact areas each have a normal that defines a plane inwhich ultrasonic signal paths of the ultrasonic signals extend, whereinthe plurality of ultrasonic transducers include a first group ofadjoining first ultrasonic transducers arranged relative to a measuringtube longitudinal section on a first side of the measuring tube, andwherein the plurality of ultrasonic transducers include a second groupof adjoining second ultrasonic transducers arranged relative to themeasuring tube longitudinal section on a second side of the measuringtube opposite the first side, wherein each coupling element of the firstultrasonic transducers and of the second ultrasonic transducers have alongitudinal axis, wherein the longitudinal axis has, in each case, aninterior angle at the corresponding second contact area, wherein theultrasonic signal path extends in the coupling element in the directionof the longitudinal axis, wherein at least one first ultrasonictransducer is adapted to receive the ultrasonic signals of at least onesecond ultrasonic transducer and vice versa, wherein the adjoiningultrasonic transducers of the first group each have a first separation,A1, from each other, and wherein the adjoining ultrasonic transducers ofthe second group each have a second separation, A1, from each other,wherein the first separation and the second separation are unequal,wherein:2*A1>=A2>=1.125*A1.
 17. The transducer arrangement of claim 16, wherein:1.6*A1>=A2>=1.25*A1.
 18. The transducer arrangement of claim 16, whereina relationship between the first separation and second separationcorresponds to the following equation:(a+1)*A1=a*A2 with b>a>1, wherein a is a natural number, and b is anupper value for a range of a and is less
 9. 19. The transducerarrangement of claim 18, wherein b is less than
 5. 20. The transducerarrangement of claim 18, wherein the first group of first ultrasonictransducers has a first number of ultrasonic transducers, and wherein asecond group of second ultrasonic transducers has a second number ofultrasonic transducers, wherein the first number is greater than orequal to a+1, and the second number is greater than or equal to a+1. 21.The transducer arrangement of claim 20, wherein the first number isgreater than or equal to a+2, and the second number is greater than orequal to a+2.
 22. The transducer arrangement of claim 18, wherein the atleast one transducer element has a radial extent, rA, wherein:rA>3/(4*a)*A1*sin(α).
 23. The transducer arrangement of claim 20,wherein:rA>1/(2*a)*A1*sin(α).
 24. The transducer arrangement of claim 16,further comprising a third group including at least a third ultrasonictransducer, which has a signal path extending perpendicular to thesecond contact area of the respective coupling element.
 25. Thetransducer arrangement of claim 16, wherein the first group of firstultrasonic transducers and the second group of second ultrasonictransducers are each held by a support body configured to position andsecure the first and second groups.
 26. The transducer arrangement ofclaim 25, wherein the first and second ultrasonic transducers are eachheld individually in the corresponding support body.
 27. A clamp-onultrasonic, flow measuring point for measuring a flow velocity of amedium flowing through a measuring tube, the measuring point comprising:a measuring tube adapted to convey a medium and having a measuring tubeaxis; an ultrasonic transducer arrangement as claimed in claim 16,wherein the ultrasonic transducer arrangement is oriented in parallelwith the measuring tube axis; and an electronic circuit configured tooperate the plurality of ultrasonic transducers and to determine andprovide measured values of a flow velocity of the medium.
 28. Themeasuring point of claim 27, further comprising a curvature sensorconfigured to determine an outer diameter of the measuring tube, thecurvature sensor including a separation sensor and a spacer, wherein thespacer has a central region and two ends adjoining the central region,wherein the ends are bounded from the central region by a bend or anangle, wherein the spacer is configured via the ends to contact themeasuring tube, wherein the central region is adapted to be spaced fromthe measuring tube, and wherein a cross-section or longitudinal sectionthrough the spacer through the two ends is configured to extend inparallel with a measuring tube cross-section, wherein the separationsensor is arranged on the spacer in the central region, and wherein theelectronic circuit is configured to operate the separation sensor. 29.The measuring point of claim 28, wherein the separation sensor is anoptical or acoustic separation sensor.
 30. A method for commissioningthe clamp-on ultrasonic, flow measuring point as claimed in claim 27,the method comprising: transmitting, simultaneously or offset in time,ultrasonic signals from each of the first ultrasonic transducers andsecond ultrasonic transducers, respectively; receiving the transmittedultrasonic signals from the first ultrasonic transducers by the secondultrasonic transducers, and receiving the transmitted ultrasonic signalsfrom the second ultrasonic transducers by the first ultrasonictransducers, respectively; and determining at least one ultrasonictransducer pair of the first and second ultrasonic transducers to beused for a measurement operation based on a signal strength and/or asignal-noise ratio of the received ultrasonic signals using theelectronic circuit.
 31. The method of claim 30, wherein the ultrasonicsignals are quasi continuous and differ in frequency, or wherein theultrasonic signals are pulsed and differ in a center frequency of afrequency spectrum.
 32. The method of claim 30, further comprising:conveying the medium through the measuring tube; examining portions ofthe received ultrasonic signals for presence of a travel timedifference; and excluding portions of the received ultrasonic signalswithout travel time difference in determining the at least oneultrasonic transducer pair to be used for the measurement operation. 33.The method of claim 30, wherein the plurality of ultrasonic transducersof the ultrasonic transducer arrangement of the clamp-on ultrasonic,flow measuring point further includes a third group of ultrasonictransducers including at least a third ultrasonic transducer, which hasan ultrasonic signal path extending perpendicular to the second contactarea of the respective coupling element, the method further comprising:transmitting and receiving a third ultrasonic signal via the thirdultrasonic transducer; determining an outer diameter and/or innerdiameter of the measuring tube based on at least one signalcharacteristic of the received third ultrasonic signal using theelectronic circuit.
 34. The method of claim 30, wherein the clamp-onultrasonic, flow measuring point further comprises a curvature sensorconfigured to determine an outer diameter of the measuring tube, thecurvature sensor including a separation sensor and a spacer, wherein thespacer has a central region and two ends adjoining the central region,wherein the ends are bounded from the central region by a bend or anangle, wherein the spacer is configured via the ends to contact themeasuring tube, wherein the central region is adapted to be spaced fromthe measuring tube, and wherein a cross-section or longitudinal sectionthrough the spacer by the two ends is configured to extend in parallelwith a measuring tube cross-section, wherein the separation sensor isarranged on the spacer in the central region, and wherein the electroniccircuit is configured to operate the separation sensor, the methodfurther comprising determining an outer diameter of the measuring tubeusing the electronic circuit based on the curvature sensor.